Mn giúp em 2 câu này với
\(c,x\left(x-20\right)-x+20=0\\ \Leftrightarrow x^2-20x-x+20=0\\ \Leftrightarrow x^2-21x+20=0\\ \Leftrightarrow\left(x-20\right)\left(x-1\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=20\\x=1\end{matrix}\right.\)
\(b,x^2-4+\left(x+2\right)\left(x-3\right)=0\\ \Leftrightarrow x^2-4+x^2-x-6=0\\ \Leftrightarrow2x^2-x-10=0\\ \Leftrightarrow\left(2x-5\right)\left(x+2\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5}{2}\\x=-2\end{matrix}\right.\)
a: Ta có: \(x\left(x-20\right)-x+20=0\)
\(\Leftrightarrow\left(x-20\right)\left(x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=20\\x=1\end{matrix}\right.\)
b: Ta có: \(x^2-4+\left(x+2\right)\left(x-3\right)=0\)
\(\Leftrightarrow\left(x+2\right)\left(2x-5\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=\dfrac{5}{2}\end{matrix}\right.\)
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